> I built a new kernel taking the source from
> ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-release-1-5
>
> is 1.5.3_ALPHA a -CURRENT release?

No.

> is it a 1.5.2 bug fix release, is it a stable release?

1.5.3_ALPHA is a marker used to mark an interim step between 1.5.2 and
1.5.3, which are all along the development branch which was created
when the release cycle for 1.5 was started, and which produced the 1.5
release and the maintenance releases 1.5.1 and 1.5.2, and from which
the 1.5.3 release will be created.  The CVS tag identifying this
branch is "netbsd-1-5".

> what is the best way to keep up to date with a stable NetBSD release
> but at the same time being able to get the latest patches for
> security etc...?  I am used to FreeBSD STABLE style in which you can
> get always an up to date and stable and bugfree source code to
> replace the default RELEASE distribution. Is there any way to do so
> with NetBSD too?

If I've understood things correctly, at present you would acheive the
same thing in NetBSD by tracking the development on the netbsd-1-5
branch.

Regards,

- H=E5vard