[abhinav22]

But isn’t PostgreSQL and (sorry if I got the name wrong) MariaDB also open source?

I think the success of SQLite is the small size / no installation, but I agree it could only become as popular as it currently is due to its open source nature.

[zhouyisu]

SQLite is good and open source. I've tried MariaDB on a Python project. The connector has bugs very hard to debug. I tried to download the python source, C++ source and failed to locate the bug. I tried to add issue but find nowhere to report. Finally I give up and use MySQL instead. It works like a charm. Open source adds value, but IMHO being good is first priority.