Once upon a time a nice program existed: the Opera browser based on the Presto rendering engine. Not everything was fine with it but many people liked it.
Then the Opera (management?) team decided that it was too expensive to maintain/develop an own rendering engine and that it was better to drop the old one in favour of Googles' Engine, Chrome.
But the people who liked Opera/Presto did not stop to like it. (I call them dreamers in the next paragraph ...)
About one time every year I asked the search engine for the "ancient" opera source. Usually there was no result despite of some new projects of those "dreamers" like Fifth and OtterBrowser. (Ironically when I tried Fifth it crashed when I visited the Fifth Github page :-) )
But this year the search engine told me that the Opera browser source was leaked which really can be considered quite exciting news!
On the official Opera (company) blog has appeared following post in January: [https://blogs.opera.com/security/2017/01/legacy-opera-presto-source-code-appearance-online-sharing-sites/]
Legacy Opera Presto source code appearance in online sharing sites
Opera recently became aware that source code from our legacy browser engine, Presto, has appeared in some online code and file sharing sites. This code is the property of Opera Software and has been published illegally and without our permission.
While some of Opera’s products are not currently fully open source, Opera has great respect for the open source community.
I guess that they are right - much of their effords are open source. And I guess it is the right thing to keep the legacy product alive.
So I have made some thoughts on the future of Opera 12.15 (= last Opera Presto for Linux). Here are the results:
The result of the legal analyses is that in EU it is no problem to correct errors and provide those patches for the public. In the USA this is partly possible. The patches have to be user-appliable to the original Opera browser binary, respectively. I didn't research the other countries' situation.
My personal opinion is that all activity about Opera/Presto shall be as open and as public as possible! A web browser is an essential part of most computer systems and therefore shall be as well documented and reviewable as the Linux kernel or the GNU tools e.g..
At last here's the graphical version of the possible patch coverage as to be found in License_and_Patch_options.ods as well:
Document of November 9, 2017, last modification on 10 November 2017. Page source