Is F# open source?

Question

Is F# open source? if not so why Microsoft provide the source code of the F#'s modules?

EDIT

(Nov 4, 2010) Things have changed, see Brian McKenna's answer.

Answer 1

It is published under a variant of the MS-Research open source licence.

I have no idea if this is "officially" open.

Answer 2

"Microsoft Research Shared Source license", under which F# is published, has not been approved by Open Source Initiative nor by Free Software Foundation (although a couple of other Microsoft licenses are).

The bottom line is that sharing the source code has little to do with making a product open source. The essential point is the license, which (dis)allows to use and modify the source more or less freely. Without such a license the source is pretty much useless.

Answer 3

f# as of the 2008 CTP release is under a slightly modified Microsoft Research Shared Source license agreement ("MSR-SSLA").

Essentially you can modify it but MS gets royalty free permission all your modifications

There was talk within the team of it moving to the more open MS-PL licence, I don't know how that has gone, nor what the implications are given the plan to include f# in VS2010.

Answer 4

Did anybody actually try to build F# from the sources included in the release? It seems to me that some parts are missing which prevent this. This is in addition to a license which is not OSI-approved. So, no, F# is not open source.

Answer 5

Right now the F# team seems pretty busy with all the "productisation" effort. One email with the plans for the licensing is here.

As we complete this over the next year, our plan is to make a corresponding source release of the F# compiler components under MS-PL.

And:

Along the way, we plan to make a source release of the MSR "Power Pack" components, also under MS-PL. These include tools such as fslex.exe and fsyacc.exe and some libraries. These may be released more often and may include experimental components.

With:

In general, we aim for the source code releases we make of F# to open, stable and correspond to supported releases.

And perhaps the nicest bit :) :

On the whole we prefer to "do" rather than "pre-announce".

I'll also note that if you're not using the term "Open Source" meaning "approved by certain organisations as Open Source", then the source code is already included with the F# distro. (And using F12 "Go To Definition" in VS will jump you right to the source files.)