This is one point over which there is some controversy. I would argue that a copyright owner merely distributing software gives one the right to use that software as it was intended, just as distributing a book gives a recipient the right to read it. A license can only restrict that right, or grant additional rights one would not have under copyright.

The GPLv3 preemptively deals with potential counterarguments to this point of view by explicitly affirming the right to use the software, but using reductio ad absurdum, it seems ridiculous to be able to distribute a work under the protection of copyright law without implicitly giving the lawful recipients of the work the ability to use it as intended.

There are plenty of examples of commercial software that is distributed by the copyright owner free-of-charge, but requests agreement to a conditional license during the installation process.

I believe that in the US, this relies on a court ruling (sorry, no cite) that as the use of software inherently requires making a copy of it, such use is a copy right. This is unlike the case of a book or a painting.

There are also examples of commercial software distributed free of charge with no license agreement whatsoever. I sincerely hope that the decision that using software is a "copy" right not implicitly granted by its distribution is overturned, as the notion is truly ludicrous.

That doesn't necessarily mean that EULAs would be unenforcable; one could still argue that the license page of the installer is an effective access control mechanism between the user and the software, possibly invoking some twisted interpretation of the DMCA.

...and I hate that I feel like I have to put this, but as I mentioned elsewhere, IANAL.