Port to Drupal 6

If necessary, yes... eventually. ;)

That said, you're probably looking for #376377: Issue + organic group incompatibility

og_project was originally written for 4.7.x OG and project*. A *lot* has changed since then. I haven't given this any real attention in literally years. one of these days, I (or someone else motivated to do so) needs to give OG + project* some serious testing and love. It's possible there's really no need for a glue module anymore (there was when I first wrote this), and that there are just a few project* bugs that could be fixed and then things will Just Work(tm). Anyway, I honestly have practically no idea what the current state of affairs is, beyond the fact that I know it's broken in D6. It's probably broken in D5, too, but I'm not sure. I just haven't had a need to play with it and see in exactly what way(s) it's broken...

Ok, I made some progress on all of this over at #376377-20: Issue + organic group incompatibility. Project* + OG is basically working now if you use HEAD of Project*. However, it's still a bit rough around the edges, and there are a few things that would be slick to get working which really belong in this glue code project, not in either Project* nor OG.

Stay tuned.

The D6 version (in HEAD) currently doesn't do anything (og_project.module is empty) but the .info file works. ;) The basics of OG + project* are working fine without this module thanks to #376377: Issue + organic group incompatibility and #405478: Do a proper page/code split of project_issue. We need to add some code here, but that needs to happen in other issues, for example, #173639: Project nodes as OG: keeping project* content associated with both project and group