Famous James Bond 007 had a license to kill; the "00" designation in his code number meant he had a sanction to apply a deadly force. In order to use any software you also need a license. Let me repeat, *any* software, even one which you can download free of charge with a couple of mouse clicks.
When accepting a license you become bounded by a legal agreement that the software is available under. Tell me honestly, how many of you and how often do you read the license agreement shown during install screen that makes you select a radio-button "Yes, I accept this license" before clicking Next? I bet very few, and I’m not a role model either ;-).
The fact that you can freely download some software does not imply you can use it and distribute your software based on it at your own wish. The most famous example is GPL'ed software (General Public License) which is known to be 'viral', i.e. making your own software GPL'ed. This at least applies to GPL version 2; version 3 comes with some more sophisticated terms which I did not fully study yet.
So, what about Open CASCADE license ? Among most important aspects, I'd underline that it's quite permissive and allows you to use OCC in your project (open or closed source, free of charge or for a fee), that can be distributed under your own proprietary license. Like most other Open Source licenses it requires that you include a copy of the license into your distribution. All modifications to Open CASCADE software you might make must be made available in source code, under the same license to anyone.
The summary on the site says it is "LGPL-like". I must confess this was my own suggested wording which we put with the web team, when I worked at Open CASCADE. We put that note to contrast it with GPL. It was based on my then knowledge of the subject. Working at Intel, where licensing issues are explained as part of mandatory trainings I now view this is not exactly the case. LGPL is still quite viral (though much less than GPL) and is not too welcomed in commercial applications. The OCC Public license has quite different focuses.
I believe the OCC license is somewhat weird and should better be changed. There are several existing widely recognized and adopted Open Source licenses. Any time the company comes out with its own 'open source' or 'public' license, it creates a headache for potential users and company's lawyers to read it and to understand implied rights and obligations. For average people (even native English speakers), juridical vocabulary is Greek. Take the Tax Code of your country, open it and start reading on an arbitrary page. I bet you will have to re-read each paragraph several times before you get an idea of what it is about, not saying a word about tiny details where, as we know, the evil is. So, if you really want to give your software into the Open Source world, you better choose something existing.
In this regard, Intel's move in 2005 was very symbolic to discontinue its own (and, by the way, recognized and approved) Open Source license. Motivation ? Exactly that, stop license proliferation and ease Intel’s software adoption. Look what other successful people or companies do – learn and do the same ;-).
So, my modest suggestion to the Open CASCADE company is to consider favoring some well recognized Open Source license and to migrate to it. This will ease OCC adoption and will benefit all parties.
We can continue discussion in comments. So feel free to throw in your ideas !