> it being open source and GPL, anybody can use it or fork it

The entire point of the EEE strategy is to capture protocols or standards, such as software developed by other companies or free software developed under the GPL. Forking isn't a relevant option, because the other parties software is not changed (it's expected to not be able to change).

From Microsoft employee Ronald Alepin's sworn expert testimony[1] in Comes v. Microsoft:

    Q. Okay. And now, again, for the Jury, what does embrace mean in
       this context as used by Microsoft employees?

    A. It's used to indicate a strategy where Microsoft will embrace
       the standards or the specifications and interfaces of another
       company's software.

    Q. Okay. And what does extend refer to?

    A. Once the specifications have been embraced, then Microsoft will
       extend them and add additional interfaces proprietary to Microsoft.

    Q. Okay. When you say add additional proprietary interfaces that
       are Microsoft's, what impact does that have technologically to
       other ISVs and OEMs?

    A. Well, the result is or the impact is that what was once sort of
       community development property, the work of the industry and
       industry participants is appropriated essentially, is taken over
       by Microsoft.

       And then Microsoft takes it and with its proprietary extensions,
       makes it essentially unavailable on a going-forward basis to the
       industry participants who were responsible for first developing
       the specifications and the standards.

    Q. Okay. And when Microsoft makes those APIs unavailable to certain
       ISVs and OEMs, what's the impact to those ISVs and OEMs of their
       ability technologically to create products?

    A. It reduces their ability to create products, especially products
       that will interoperate with Microsoft's products.

Examples of this strategy include Mirosoft's attempts to capture the Kerberos protocol and Java. In both examples Microsoft first embraced existing software outside their control by writing their own implementation, then added non-standard features that were only available in their implementation and a clause in their EULA that forbid anybody that used their implementation from re-implementing the features in other (original) software. The GPL doesn't help here, because Microsoft never touched the original free/open implementation, which continued to exist but was now incompatible with Microsoft's software.

While the systemd situation is a little different (it isn't trying to take over "another company's" software, systemd de facto IS somewhat similar to the EEE strategy. They initially embraced existing open standards common in Linux distros, and then extended various parts of their implementation intentionally[2] incompatible changes that had the de facto effect of "reduc[ing] [the] ability to create [non-systemd distros], especially [distros] that will interoperate with [systemd]"[3]. It's not exactly EEE, but there are strong similarities with new features used as a barrier to interoperability.

[1] http://www.groklaw.net/articlebasic.php?story=20070108020408...

[2] e.g. GNOME depending on the systemd-specific version of existing features that made running GNOME without systemd very difficult.