Is "disclude" a word and what authority says a word is a word or isn't?

So far this is what I found from Wiktionary and Merriam-Webster except the latter doesn't have disclude.

• Exclude — To keep something out.
  From Latin excludere, from ex-, “out”, + variant form of the verb claudere, “to close”.
• Preclude — To prevent something from happening.
  From Latin praeclūdere, “to shut up”, from prae- + claudere, “to close”.
• Disclude — To shut apart.
  Latin discludere, “to shut apart”.

About the second question :

1- In countries like the English-speaking ones, there is no overall regulation ; a word becomes part of the language if it is used and generally understood, especially when forged by a recognized writer, who gives him some right to live (about one third of the words, in Shakespeare, were invented by him, and many are still in use).

2- In countries like the French-speaking ones, there is an Academy supposed to rule both vocabulary and syntax. In fact their works are very slow (they study every word one by one in alphabetic order, returning to the beginning takes 26 years ! - what about new words appearing just too late ?), and the members are elected more for political motives than real competence - some have hardly written anything). Before the institution by Richelieu (who thought he was himself a distinguished linguist bus was deeply mistaken), the situation was sounder, the language was living and burgeoning, with authors like Rabelais for instance. Now, de facto, French is ruled by two commercial publishers : Larousse and Robert ; each year, they allow new words or suppress obsolete ones, just following the use, without any real criterion - except to publish a new, updated, reference book you must buy.

"Exclude" is keeping the thing outside of the castle walls (wherein you are).

"Disclude", properly, is a setting-apart – e.g., the guy in the jail cell.

My feeling is that "Disclose" is sufficient for the purpose of meaning "revealing/stating of information" (and that "Divulge" is distinct in that it connotes the revealing of information sensitive in nature).

Using "Disclude" to mean "Disclose" is as clumsy as putting lipstick on a cat.