I was asked recently why I tell users of Microsft Windows Operating Systems to use the hard-drive defragging program MyDefrag over Piriform Defraggler. Afterall, I point users to Piriform's CCleaner just as often as I point at MyDefrag.
I addressed the reason somewhat in the guide I wrote a few years back on JkDefrag, which turned into MyDefrag. JkDefrag was released under an Open-Source license. Unfortantly, MyDefrag, is not released under an Open Source License.
However, Piriform's Defraggler doesn't even have a listed license. Wikipedia simply states that the software is licensed as Freeware.
Between the two, I know where I stand on MyDefrag's license. I don't agree with the conversion from an Open-Sourced license to a closed license, but at least I know what that license is, and what it says. I can't say the same about Piriform's Defraggler.
The reason I have no qualms about Piriform's CCleaner is this: As far as I'm aware there are no clearly licensed, open-sourced or otherwise, tools that can replace Microsoft's Disk Cleanup utility. In this light Piriform's lack of a clearly stated license on CCleaner is an overlookable issue.