Searching the http://patents.stackexchange.com site, I found a question that linked here:
An open source program can infringe a patent just the same as a
commercial one. There is no requirement that the infringement be for
profit, since infringement may consist of making, using, selling,
offering to sell, or importing the invention. 35 U.S.C. § 271.
Infringement may be direct (i.e. the author making the software) or
indirect (e.g. the author distributing it to others intending that
they use it in an infringing manner).
What's more, by copying a program knowing that it likely infringes a
patent, the open source author may be liable for willful patent
infringement. That carries with it the possibility of treble damages
and an award of attorney's fees and costs. 35 U.S.C. § 284.
So yes, it appears as though Bitcoin developers could be held liable.
The article also continues to state that it is often not financially feasible for patent holders to go after open source software, since software is global but patents vary country to country. Also, there are not necessarily assets to be won from open source developers.
Personally, I feel that Craig Wright has been applying for patents not to target Bitcoin, but the growing blockchain industry. The banks and financial institutions adopting blockchain solutions do have assets that can be easily won (or settled) with patent suits.
DISCLAIMER: I am not a lawyer, and am way out of my element with this answer :)