In the style of a Miss Manners letter, since this is an etiquette question.

Dear Miss FOSS,

I love an Open Source project that seems to have stagnated recently. It's well designed, and I use it daily. Let's call it Hank. It has not had a new release in a year, has over a thousand issues and over 500 waiting PRs. I am considering forking, so that I can add the features to it that I want. Part of those features though is making use of some of those PRs.

My question to you is, if I fork Hank, is it a no-no to bring those PRs along, and should I contact each PR submitter individually to ask their permission?

Thank you for your help,

Stymied in Software Limbo