I forked a SVN project on GitHub some 2 months ago, using git-svn (git svn rebase), and made my changes, sending some (but not all) via patch files back.
Now the project moved to GitHub, is there any way I can merge these two GitHub projects while keeping my fork’s history?
If the import has been done properly, the SHA1 for the content imported on GutHub from SVN should be the same than the SHA1 generated by your git-svn fork on GitHub.
If that is the case, then “Merging between forks in GitHub” is your answer (or “Merge changes from remote GitHub repository to your local repository“).
If not, it is best to recreate your fork from the official GitHub repo, and re-apply your work as patches on top of said new fork.