If there are some custom plugins or reusable code I usually build my stuff on, can they be reused in jam or I should build from scratch?
That's totally fine! As long as the tools are open sourced so technically anyone can use them if they desire. It wouldn't make a lot of sense for me to have to rewrite all my general post processing shaders right, cause I'd just rewrite the exact same code lol. If it's a really complex and unique tool that you aren't comfortable open sourcing but want to show off, you can tell me about it and I can give exceptions.