I've always wondered why the creator of SQLite (who's also the creator of Fossil SCM) will state that SQLite is not meant for client/server scenarios ... yet his Fossil SCM (which is client/server) uses SQLite.
It is fine to use SQLite as the local storage in the implementation of some custom server like Fossil, as there is a separate server (Fossil) that sits in between the client and the data. In fact, SQLite excels at this and usually works better than traditional client/server databases. The scenario you want to avoid is where the client attempts to access SQLite data directly across the network, with no intermediary server. The proverb is: "Always send your query to the data, not the data to the query."
It will work to access an SQLite database across a network filesystem. Just remember that the amount of information that flows between the SQL engine and the storage medium is much greater than the amount of information that flows between the SQL engine and the application. So if the storage is separated by from the application by a relatively slow network, you want to position that network on the low-bandwidth link to obtain the best performance. That means that the SQL engine needs to be on the same side of the network as the storage - hence a client/server database. If you use SQLite to access a network file, the SQL engine will be on the application side of the network and a lot more content will need to traverse the relatively slow network link.
And so, while SQLite will work in a client/server situation, you might be disappointed by the resulting network load and/or performance of the system.
In the case of Fossil, Fossil itself is the "client" for SQLite and it is on the same machine as the data, which is exactly what you want with SQLite. The client of the Fossil server might well be across a network, but that does not matter to SQLite.
So how is what you described above architecturally different than a web application architecture?
Which is a use case I thought you did not recommend.
It places no restrictions whatsoever on the applications that uses it. That will be pointless. Fossil-SCM uses SQLite and is itself client server.
But, our desire for both simplicity and obscenely low latency means that SQLite is still the better choice for us at the moment. In the future, though, I can see robust concurrency support being important even in single application use-cases.
Note that this is very much in line with their recommendations from the docs (http://sqlite.org/whentouse.html):
>>SQLite is not directly comparable to client/server SQL database engines such as MySQL, Oracle, PostgreSQL, or SQL Server since SQLite is trying to solve a different problem.
Client/server SQL database engines strive to implement a shared repository of enterprise data. They emphasize scalability, concurrency, centralization, and control. SQLite strives to provide local data storage for individual applications and devices. SQLite emphasizes economy, efficiency, reliability, independence, and simplicity.
SQLite does not compete with client/server databases. SQLite competes with fopen().<<
It's worth noting that when considered as competition to fopen(), SQLite is quite good.