How to migrate from sourceforge to github ?

More generally, you should be able to adapt this procedure to migrate any SVN repository to GIT.

git-svn clone \
    --prefix=svn/ --stdlayout --authors-file=./phpfreechat_authors_file \
    https://phpfreechat.svn.sourceforge.net/svnroot/phpfreechat/ phpfreechat
git clone http://github.com/nothingmuch/git-svn-abandon.git
cd phpfreechat
../git-svn-abandon/git-svn-abandon-fix-refs
git remote add origin git@github.com:kerphi/phpfreechat.git
git push --all
git push --tags

./phpfreechat_authors_file should contains data formated like this :

pseudo1 = Name Surname <mail@domain>
pseudo2 = Name2 Surname2 <mail2@domain2>