The large number of empty repositories can be explained by the fact that in the old days, for each project, repositories were created for CVS and Subversion. No project starts using both and in recent years many projects chose to use Mercurial, Darcs or Git.
If nobody objects, I'll remove the list of directories below on Saturday March 28th.
/project/able/svn
/project/adw-charting/svn
/project/ait/svn
/project/alexandria/svn
/project/anaphora/svn
/project/araneida/svn
/project/armish/svn
/project/arxana/svn
/project/asdf-binary-locations/svn
/project/asdf-packaging/svn
/project/asdf-system-connections/svn
/project/asia/svn
/project/aspectl/svn
/project/aspiwork-pdm/svn
/project/babel/svn
/project/bayescl/svn
/project/bdb/svn
/project/beep/svn
/project/beirc/svn
/project/berkeley-db/svn
/project/bese/svn
/project/boston-lisp/svn
/project/bpm/svn
/project/buclet/svn
/project/bytemap/svn
/project/c2ffi/svn
/project/cdr/svn
/project/cello/svn
/project/cells/svn
/project/cells-gtk/svn
/project/cells-ode/svn
/project/cffi/svn
/project/chemboy/svn
/project/chtml-matcher/svn
/project/cinline/svn
/project/cl-amqp/svn
/project/cl-api/svn
/project/clappa/svn
/project/cl-applescript/svn
/project/clazy/svn
/project/cl-berkeley-db/svn
/project/cl-bio/svn
/project/cl-blog/svn
/project/cl-buchberger/svn
/project/clbuild/svn
/project/cl-bzip2/svn
/project/cl-cactus-kev/svn
/project/cl-captcha/svn
/project/cl-carbon/svn
/project/cl-clickatell/svn
/project/cl-cli-parser/svn
/project/cl-cont/svn
/project/cl-couch/svn
/project/cl-cracklib/svn
/project/cl-date-calc/svn
/project/cl-dbf/svn
/project/cl-def/svn
/project/cl-dises/svn
/project/cldoc/svn
/project/cl-dwim/svn
/project/cl-ec2/svn
/project/cl-emb/svn
/project/cl-enumeration/svn
/project/cleric/svn
/project/cl-fltk/svn
/project/cl-fuse/svn
/project/cl-gdbm/svn
/project/clget/svn
/project/cl-glpk/svn
/project/cl-godb/svn
/project/cl-graph/svn
/project/cl-graphviz/svn
/project/cl-gsl/svn
/project/cl-gtk2/svn
/project/cl-hooks/svn
/project/clhp/svn
/project/cliki/svn
/project/climacs/svn
/project/clim-desktop/svn
/project/climplayer/svn
/project/cl-interpol/svn
/project/cl-ipc/svn
/project/cl-irregsexp/svn
/project/cl-jpeg/svn
/project/cl-json/svn
/project/clkd/svn
/project/cl-l10n/svn
/project/cl-launchpad/svn
/project/cl-lazy-list/svn
/project/cl-lexer/svn
/project/cl-librarian/svn
/project/cl-machine-learning/svn
/project/cl-magick/svn
/project/cl-markdown/svn
/project/cl-match/svn
/project/cl-mathstats/svn
/project/cl-memcached/svn
/project/cl-menusystem/svn
/project/cl-migrations/svn
/project/cl-mp3-parse/svn
/project/cl-mpd/svn
/project/cl-mpi/svn
/project/cl-muproc/svn
/project/cl-objc/svn
/project/cl-octave/svn
/project/cl-ode/svn
/project/clois-lane/svn
/project/clonsigna/svn
/project/cl-opengl/svn
/project/cl-openid/svn
/project/cl-org-mode/svn
/project/closer/svn
/project/closure/svn
/project/clotnet/svn
/project/clouchdb/svn
/project/cloud/svn
/project/cl-pdf/svn
/project/cl-peg/svn
/project/cl-perec/svn
/project/cl-plplot/svn
/project/cl-plus-j/svn
/project/cl-plus-ssl/svn
/project/cl-pop/svn
/project/cl-ppcre/svn
/project/cl-prevalence/svn
/project/cl-proc/svn
/project/clpython/svn
/project/cl-quasi-quote/svn
/project/cl-rdbms/svn
/project/cl-rope/svn
/project/cl-rundown/svn
/project/cl-sbml/svn
/project/cl-screen/svn
/project/cl-selenium/svn
/project/cl-semantic/svn
/project/cl-serializer/svn
/project/cl-smogames/svn
/project/cl-smtp/svn
/project/cl-snmp/svn
/project/cl-soap/svn
/project/cl-sockets/svn
/project/clsql-fluid/svn
/project/cl-sqlite/svn
/project/clsql-mysql-introspect/svn
/project/cl-stm/svn
/project/cl-stomp/svn
/project/cl-store/svn
/project/cl-syntax-sugar/svn
/project/cl-syslog/svn
/project/cl-taint/svn
/project/cl-telnetd/svn
/project/cl-test-grid/svn
/project/cltl3/svn
/project/cl-trane/svn
/project/cl-twitter/svn
/project/cl-typesetting/svn
/project/cl-unification/svn
/project/cl-uri/svn
/project/cl-utilities/svn
/project/cl-variates/svn
/project/cl-walker/svn
/project/cl-wav-synth/svn
/project/cl-weblocks/svn
/project/cl-who/svn
/project/cl-wiki/svn
/project/cl-x86-asm/svn
/project/cl-xmlspam/svn
/project/cl-xmms/svn
/project/cl-xmpp/svn
/project/cl-yacc-ebnf/svn
/project/commonqt/svn
/project/computed-class/svn
/project/core-services/svn
/project/corman-sdl/svn
/project/cparse/svn
/project/crypticl/svn
/project/css-sexp/svn
/project/cxml/svn
/project/decl/svn
/project/defclass-star/svn
/project/defdoc/svn
/project/defeditor/svn
/project/definer/svn
/project/defmud/svn
/project/defplayer/svn
/project/defwm/svn
/project/de-setf-graphics/svn
/project/docudown/svn
/project/docutrack/svn
/project/drakma/svn
/project/dynamic-classes/svn
/project/eager-future/svn
/project/ecl/svn
/project/eclipse/svn
/project/ecl-readline/svn
/project/elephant/svn
/project/encline/svn
/project/erlang-in-lisp/svn
/project/erlisp/svn
/project/external-program/svn
/project/f2cl/svn
/project/fiveam/svn
/project/flexichain/svn
/project/fret/svn
/project/ftd/svn
/project/fucc/svn
/project/gamelib/svn
/project/ganelon/svn
/project/geco/svn
/project/gecol/svn
/project/geohash/svn
/project/gestalt/svn
/project/ginseng/svn
/project/glouton/svn
/project/gnucard/svn
/project/grand-prix/svn
/project/gsharp/svn
/project/gtk-cffi/svn
/project/gzip-stream/svn
/project/html-template/svn
/project/hyperdoc/svn
/project/hyperspec-lookup/svn
/project/iaxphone/svn
/project/ieee-floats/svn
/project/ieeefp-tests/svn
/project/imago/svn
/project/innen/svn
/project/ip-interfaces/svn
/project/iso8601-date/svn
/project/israel-lisp/svn
/project/iterate/svn
/project/iterate-clsql/svn
/project/jess-parse/svn
/project/jnil/svn
/project/kpax/svn
/project/lambda-gtk/svn
/project/langutils/svn
/project/lgtk/svn
/project/liards/svn
/project/lifp/svn
/project/limp/svn
/project/lineal/svn
/project/linedit/svn
/project/lispbox/svn
/project/lispfaq/svn
/project/lisp-interface-library/svn
/project/lisp-matrix/svn
/project/lisp-on-lines/svn
/project/lisppaste/svn
/project/lisp-res-kit/svn
/project/lispy/svn
/project/l-math/svn
/project/lmud/svn
/project/local-time/svn
/project/log4cl/svn
/project/log5/svn
/project/lw-vim-mode/svn
/project/macho/svn
/project/macondoolap/svn
/project/magicffi/svn
/project/mcclim/svn
/project/mel-base/svn
/project/metacopy/svn
/project/meta-cvs/svn
/project/metatilities/svn
/project/metatilities-base/svn
/project/mirror/svn
/project/misrouted/svn
/project/mkcl/svn
/project/mk-defsystem/svn
/project/modisc/svn
/project/mod-lisp/svn
/project/movies/svn
/project/movitz/svn
/project/named-readtables/svn
/project/names-and-paths/svn
/project/new-op/svn
/project/nixies/svn
/project/noctool/svn
/project/nrw-xmcl/svn
/project/objective-cl/svn
/project/oct/svn
/project/okra/svn
/project/openair/svn
/project/osicat/svn
/project/pal/svn
/project/parenscript/svn
/project/parse-declarations/svn
/project/patty/svn
/project/pg/svn
/project/pg-introspect/svn
/project/phemlock/svn
/project/phorplay/svn
/project/plexippus-xpath/svn
/project/ply/svn
/project/portage-overlay/svn
/project/postmodern/svn
/project/pretty-function/svn
/project/protobuf/svn
/project/quiz/svn
/project/rcl/svn
/project/rclg/svn
/project/rfc2109/svn
/project/rfc2388/svn
/project/rfc2822/svn
/project/rjain-utils/svn
/project/rucksack/svn
/project/same/svn
/project/sapaclisp/svn
/project/sb-simd/svn
/project/sequence-iterators/svn
/project/sexpc/svn
/project/sfip/svn
/project/sheeple/svn
/project/sicl/svn
/project/slime/svn
/project/snmp1/svn
/project/sparklines/svn
/project/spray/svn
/project/sqlisp/svn
/project/ssc/svn
/project/stamp/svn
/project/stdutil/svn
/project/stefil/svn
/project/suave/svn
/project/submarine/svn
/project/sudoku/svn
/project/s-xml/svn
/project/s-xml-rpc/svn
/project/teepeedee2/svn
/project/tinaa/svn
/project/tioga/svn
/project/trivial-features/svn
/project/trivial-freeimage/svn
/project/trivial-garbage/svn
/project/trivial-gray-streams/svn
/project/trivial-http/svn
/project/trivial-iconv/svn
/project/trivial-timeout/svn
/project/trivial-utf-8/svn
/project/ubf/svn
/project/ucs-sort/svn
/project/ucw/svn
/project/ucw-extras/svn
/project/umpa-lumpa/svn
/project/unetwork/svn
/project/uri-template/svn
/project/vial/svn
/project/vivace-graph/svn
/project/wispylisp/svn
/project/xcvb/svn
/project/xhtmlambda/svn
/project/xml-psychiatrist/svn
/project/xmls/svn
/project/xuriella/svn
/project/zip/svn
/project/zlib/svn