The MIT License (MIT)
Copyright (c) 2009-2019 The Bitcoin Core developers
Copyright (c) 2009-2019 Bitcoin Developers
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
refI think this answers the question... but there's a difference between patents and copyright.
Patenting is protecting an idea and copyrighting is protecting the acutal body of code.
If this agreement that they agreed to when they downloaded the software then they are still bound by it, particularly
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
So depending on how much was copied then the license still applied (if thye took a part of the software, such as the hashing algorithm or signature algorithm) they'd have no conflicts with this software (potentially) but may be bound by the copyright of any software/references that are in that part of the code...
Blockchains must have had a theoretical foundation a while ago and hashcash wasn't released with any patent, if this was patented then a filing may be put in place for infringement of anothers' intellectual property.