Palette works. Please take into SVN, because I have it permanently integrated into the German language files.

In ContextHelp.lng you no longer need the lower section that creates the javascript hash.
This means you can add items to %contextxt by using the

$contextxt{'newmod'} = 'New Mod Context Help'; 

above the 1;

for offtopic it's:

$contextxt{'offtopic'} = "Mark an Off Topic Comment:<br /><br />Select the text: bla bla [SELECT]Hello World[/SELECT] bla bla<br /><br />Click on the \"[TITLE]\" button: [BUTTON]<br /><br /><b>YaBBC Code:</b> bla bla 
Off Topic Comment
Hello World
 bla bla<br /><br /><b>Result:</b> bla bla 
Off Topic Comment
Hello World
 bla bla"; 

And I'm in the middle of updating a 2.6.0 forum that has a lot of mods. Off-Topic is one of them.

I did not mean now. Both write to the ContextHelp.lng and has undergone major change. Let's see, maybe I get it out, yes.

Replace the graphics in ModImages and change the graphics names extensions in PostBox.pm to png

I've got a fix for the Palette:
In Post.lng find the 1; and add above it

$post_txt{'palette'} = 'Change Text Color';
  

In PostBox.pm find

                <span class="ubbcbutton ubbcbuttonback"><img src="$yyhtml_root/UBBCbuttons/palette1.png" class="cursor" onclick="window.open('$scripturl?action=palette;task=post', '', 'height=308,width=302,menubar=no,toolbar=no,scrollbars=no')" alt="" /></span> 

and replace with

                <span class="ubbcbutton ubbcbuttonback"><img src="$yyhtml_root/UBBCbuttons/palette1.png" class="cursor vtop" onmouseover='contextTip(event, this.alt);' onmouseout='contextTip(event, this.alt);' oncontextmenu='if(!showcontexthelp(this.src, this.alt)) return false;' onclick="window.open('$scripturl?action=palette;task=post', '', 'height=308,width=302,menubar=no,toolbar=no,scrollbars=no')" alt="$post_txt{'palette'}" /></span> 

Now, why this was missing in 2.5AE, I don't know. But this looks like one of those cases where an omisson just kept being carried into new versions.

I haven't had a chance to check the UBBC mods

Oh yeah, spoilers and off-topic must now be adjusted.

Since you can just do anything. It's not vital.

The ContextHelp on Palette has never worked as near as I can find. Even though the language is there.

Works. Now it only context-sensitive help. Which is not shown, but is available in the language file.

'palette1' => "Choose text color:<br /><br />Select the text: bla bla [SELECT]Hello World[/SELECT] bla bla<br /><br />Click on the \"[TITLE]\" button [BUTTON] and pick one of the 228 ready made colors or create a custom color tag\.<br /><br /><b>YaBBC Code:</b> bla bla Hello World bla bla<br /><br /><b>Result:</b> bla bla Hello World bla bla", 

in PostBox.pm find

                <span class="ubbcbutton ubbcbuttonback"><img src="$imagesdir/UBBC/palette1.png" class="cursor" onclick="window.open('$scripturl?action=palette;task=post', '', 'height=308,width=302,menubar=no,toolbar=no,scrollbars=no')" alt="" /></span> 

replace with

                <span class="ubbcbutton ubbcbuttonback"><img src="$yyhtml_root/UBBCbuttons/palette1.png" class="cursor" onclick="window.open('$scripturl?action=palette;task=post', '', 'height=308,width=302,menubar=no,toolbar=no,scrollbars=no')" alt="" /></span> 

It's also in the SVN. 

Okay so far, only the button for the color palette is not displayed correctly.

Just fixed in the SVN.  (And this was AFTER I tested the freaking thing.)

ARGH!!!

The backgrounds are in the download. But it looks like the CSS is wrong.
in default.css find

.ubbcbuttonback {
     background-image: url(./default/UBBC/ubbc2.png);
 } 

replace with

.ubbcbuttonback {
     background-image: url(../../UBBCbuttons/ubbc2.png);
 } 

Now I do not know if I have the correct version.
I downloaded the SVN Build 1611.
I see now UBBC buttons that are not here yet.
In addition, the button for the pallet is missing.
See picture.