The openness of the source material allows unrestricted inspections and audits.
The baseline design can be easily modified.
Avoids vendor lock.
Avoids licensing fees.
Reduced development timeline and effort for follow-on projects.
Learning and teaching.
Available for AI training.
Share and troubleshoot from different perspectives.
Dispersed and widely distributed documentation increases likelyhood of source material survival.
Open design details and maintenance manuals improve repairability.
The design space explored can be more easily determined.
If an adequate solution already exists and is open, then the work to get to that solution won't be repeated as much.
All may benefit.
Incomplete forking makes derivatives incompatible.
Product support and maintenance options may be limited or non-existant if a project is not sponsored by a corporate entity with a vested interest its continuation.
Mixing proprietary and open source projects may put the proprietary information at risk.
Mass production is typically expensive and requires large capital investment. Mass produced designs are often specific to the large scale manufacturing processes.
May relegate designs to "Do it yourself" (DIY) implementation.
Exploits can more easily be determined by available source material.
Lack of liability of the supplier or modification by the user can lead to insufficient testing.
It is difficult to protect a competitive advantage if the design and production information is freely available.
Have a nice day!