I am not a lawyer, but I have created an agreement for those instances where you want to allow someone to use your script for free. So far, it has worked well for me. Feel welcome to use it:

All good advice - below is an agreement I created and have been using if anyone is interested in copying it for their own use:

PREAMBLE

There is an agreement below. What it means is that you get to make a film from my script for free. However, I retain ownership of the script unless at some time in the future you decide to pay me for the script, and I decide to accept your offer. It is crafted in a way to allow students and new filmmakers a chance to film something at no cost for the written material.  Here are the terms:

AGREEMENT

I, David Lambertson, the WRITER, grant  NAME, THE FILMAKER, permission to use my screenplay TITLE to create a film version of the story.  No payment is required for this permission.

This permission is not intended to transfer rights to the script or otherwise create an option to own the script. It is simply intended as permission to film the story. This means:

•     The script remains the property of David Lambertson.
•     David Lambertson at his sole discretion may allow others to use the script.
•     David Lambertson may sell the script at any point in the future.
•     At any time, David Lambertson may submit this script to contests at his discretion and any and all proceeds from contest awards are 100% his.

Nothing in the above is intended to impede or restrict the filmmaker’s ownership of their completed film or infringe on their rights to those products. In other words, if the filmmaker completes a film based on the free permission granted to use the script, any subsequent use,  sale or option of the script by David Lambertson to any party does not infringe on the filmmaker’s use of the script for their film.

Unless otherwise indicated below, the filmmaker is entitled to all proceeds and awards from festivals that the completed film is submitted to other than any and all awards that directly relate to writing. Those belong the David Lambertson.

David Lambertson will receive sole and full writing credit for the script and will be recognized in the credits as the sole writer on the filmed version as well as in any future marketing efforts, submittals to film festivals, IMDB profiles, and all other public displays of the script or the films.
No changes or modifications to the script will in any way create a co-writer credit. David Lambertson is the sole writer.

The filmmaker agrees to complete the films within twelve months of receiving this permission and will provide David Lambertson access to the completed project through either a hard copy (DVD) version or a link to a website hosting the film.  

The filmmaker may at any time within twelve months tender an offer to David Lambertson to option or purchase the rights to the script. Whether to accept such an offer will be at the sole discretion of David Lambertson.

Should the film not be completed within twelve months the permission to use the scripts is revoked.

This is great, Dave!
Thank you.

Quoted from LC This is great, Dave! Thank you.

My pleasure

Awesome! Thanks for this, Dave!

Quoted from Zack Awesome! Thanks for this, Dave!

my pleasure

David, thank you for allowing me to use this contract. I'm sure it will become invaluable.


Bless.


John Stone

Quoted from Shakespeare on Toast David, thank you for allowing me to use this contract. I'm sure it will become invaluable. Bless. John Stone

My pleasure