User Content Alpha does not make files "Read Only." It simply redirects the the place Blockland will check for whatever custom UIs or textures you may have. I have written a simple guide to replacing the brick textures, since this is what User Content Alpha is commonly used for.
Click the images for a full-sized version.

First, lets take a look at where the default brick textures are located. They are stored in
Documents/Blockland/base/data/shapes/. This is important to know where they are located, you will need the folder names later on.

Before we do anything else, make sure you have placed
Client_UserContent in your Add-Ons folder.

Now, go back to the main Blockland directory. From there, open the folder
config.

Once you open the
config folder, create a new folder titled
content. This is the main folder that User Content Alpha uses.

Now this is where the folders I mentioned before come in place. You're going to want to recreate that set of folders. While still inside the
content folder, create a new folder titled
data.

Inside the newly created
data folder, create another new folder titled
shapes.

Finally, open up the
shapes folder. This is where you will place your custom brick textures. The same goes for any other texture or UI replacements, it just varies on what folders they are in by default.
Hopefully this has helped create a better understanding on using User Content Alpha and replacing your brick textures without having to use a "Read Only" workaround - which I do not recommend.