There are bits that ship with VS2010 (e.g. compiler, IDE, ...). They're subject to the VS2010 license, which is presumably somewhat restrictive.
There is the F# Runtime (FSharp.Core.dll), which is a redistributable package. You can e.g. chain it into the install/setup of your own app.
There is the F# CTP. It essentially contains the same bits as the VS release, minus the VS IDE support. It also has source code. It's under the MS Research license, which is less restrictive.
There is the PowerPack, a library with source, I forget what license it has.
In the future, there may be an open-source release of the compiler, which would be like the CTP, but with an even more permissive license (the kind of license the FSF folks like).
In general, with each download, there should be an accompanying license which you can read.
EDIT
(November 4, 2010) Now the F# compiler/runtime source is available under the Apache license, see here:
其他人回答了有关当前许可证的问题。我要指出的是，根据 FSF 和 OSI 的定义，它既不是免费的也不是开放的。除其他外，它具有严格的非商业限制。例如，您不能出于商业目的分发源代码。
只有两种免费的 Microsoft 许可证：Microsoft 公共许可证和 Microsoft 互惠许可证。
Other people answered with regard to the current license. I'll note that it is neither free nor open as defined by the FSF and OSI. Among other things, it has serious non-commercial restrictions. E.g. you can't distribute source code for commercial purposes.
There are only two free Microsoft licenses, the Microsoft Public License and Microsoft Reciprocal License.
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自 2010 年 11 月 4 日起，F# 编译器和标准库可根据 Apache 2.0 许可证从 Microsoft 获取。 FSF 认为该许可证免费且与 GPLv3 兼容。
代码为也可作为 Github 项目，位于 相同的许可证。
As of 2010-11-04, the F# compiler and standard library are available from Microsoft under the Apache 2.0 license. The FSF considers this license free and compatible with the GPLv3.
The code is also available as a Github project, under the same license.
(IANAL)
我认为简短的答案是
一般来说，每次下载都应该有一个您可以阅读的随附许可证。
编辑
（2010 年 11 月 4 日）现在 F# 编译器/运行时源可在 Apache 许可证下使用，请参阅此处：
http://blogs.msdn.com/b/dsyme/archive/2010/11/04/announcing- the-f-compiler-library-source-code-drop.aspx
(IANAL)
I think the short answer is
In general, with each download, there should be an accompanying license which you can read.
EDIT
(November 4, 2010) Now the F# compiler/runtime source is available under the Apache license, see here:
http://blogs.msdn.com/b/dsyme/archive/2010/11/04/announcing-the-f-compiler-library-source-code-drop.aspx
其他人回答了有关当前许可证的问题。我要指出的是，根据 FSF 和 OSI 的定义，它既不是免费的也不是开放的。除其他外，它具有严格的非商业限制。例如，您不能出于商业目的分发源代码。
只有两种免费的 Microsoft 许可证：Microsoft 公共许可证和 Microsoft 互惠许可证。
Other people answered with regard to the current license. I'll note that it is neither free nor open as defined by the FSF and OSI. Among other things, it has serious non-commercial restrictions. E.g. you can't distribute source code for commercial purposes.
There are only two free Microsoft licenses, the Microsoft Public License and Microsoft Reciprocal License.
是的，仍然是 具体参见此处 此链接
Microsoft Research 共享源许可协议
（F# 编译器的非标准）
<
当然，部分 .Net 库并未涵盖。
Yes, still is see here specifically this link
Microsoft Research Shared Source License Agreement
(NON-STANDARD FOR F# Compiler)
<
Of course, parts of the .Net libraries aren't covered.
查看 下载页面。仍在 SSLA 之下。
Take a look at a license link on the download page. Still under the SSLA.