This may help some to understand.
EE have to sign FAAs before Dec 1st, or they cannot be back counted for 2013.
EE that sign after Dec 1st will still be EE, but count to 2014. (They can still enroll for spring, and be in practice)
Recruits that sign LOI after Feb count as normal for 2014.
"Blue shirt" do not sign, they enroll for spring classes. They can be given a scholarship before May 31st, and count to 2014, or after May 31st and can be counted to 2015.
***note blue shirt players can be on other non athletic scholarship during that time... I.e. the legacy scholarship, or academic, as long as it is not athletic scholarship. This allowance is why the player cannot have been "recruited" and my not have taken an OV on the school's dime.
GS, also do not sign. They automatically count to 2015, as they sign FAA. They can enroll anytime after Dec 1st 2014, and be an EE for 2015.
Preferred Walk on, these are very similer to GS, but are not garanteed a scholarship, but almost always get one. In some rare cases can qualify for partial non athletic scholarship.
Walk on, these pay their way. In some rare cases can qualify for partial non athletic scholarship. If they ball like a grown man, they can earn a scholarship.
The partial scholarship must be a state, or national accredited Financial Assistance Scholarship. There are very strict rules for these, and almost any player that has a scholarship offer from any school would be rejected. I think Yale, and Harvard are the only school I can recall ever being able to field a football player that was on a non athletic scholarship.
I hope this helps, and is accurate to the best of my knowledge.
I am not 100% on the date cut off times, but the rest is as close as it gets while trying to put the rules in easy to understand language..