For your application you may want to use agar.
It is easy to find, gels at room temperature, and will remain so to about 90C.
The acidity of the orange juice will slowly (a few days) break down the agar, but it should give you enough time for a dish.
Other agents include: sodium alginate carrageenan xantham gum
A good description of the gelling agents from a cooking perspective can be found in the sites on molecular gastronomy such as tech blog of the French Culinary Institute or Martin Lersch's hydrocolloid recipe collection.
cooking.stackexchange.com/users/183/papin
Corn starch will set acid fruit to a soft jelly, but it will go very soft at high temperatures.
If you coat sweet moulds with chocolate and cool them well, you can fill them quite successfully with cooled but not yet set jellies.
cooking.stackexchange.com/users/None/
You might try modified tapioca starch, if you can heat the base of the jelly enough to set the starch; I've only used the regular form, but the processing of "modified" tapioca is supposed to remain stable at temperature (somewhere near 50C)
I'm also not sure how well tapioca handles acids (which 'orange jelly' might be); I know agar has issues with acid.
For a list and description of alternative gelling agents, see Cook's Thesaurus:
Gelatins (and possibly, Starch Thickeners )
cooking.stackexchange.com/users/67/Joe
The only ones I'm familiar with are" Leaf gelatine - made from animal protein Powdered gelatine - made from animal protein
Agar Agar - made from seaweed Arrowroot - made from plant material
Pectin - made from plant material Any of the above are, suitable for making a variety of items.
such as jam, jellies, marmalades etc.
The degree of 'firmness' of the product is related to the quantity of gelling agent to the amount of water.
cooking.stackexchange.com/users/115/Pulse
I haven't used it, but I've heard that Agar-agar can be used to solidify hot things.
cooking.stackexchange.com/users/122/jumoel
I recently was making some orange jelly which was going to be dipped in chocolate.  I couldn't use gelatine to set the jelly as it returned to a liquid below the temperature of the melted chocolate.  What other gelling agents could I have used, and what are their properties?  I'd like to expand my knowledge of what does what so I can choose the best agent for setting a jelly in a particular situation.
What are alternative gelling agents to gelatine? And what are their properties?
cooking.stackexchange.com
<substitutions><gelling-agents><gelatin>
cooking.stackexchange.com/questions/725
cooking.stackexchange.com/users/210/Sam Holder
Agar and tapioca starch can remain solid at higher temperatures, but cornstarch will go soft. Increasing the amount of gelling agent will increase the firmness. You can make firmer jellies by adding more setting agent. Agar agar would work well in this case. You can also use corn starch and modified tapioca.
Agar agar is very useful in jellies. Corn starch will work for soft jellies. You can also try tapioca starch. The firmness of the jelly will depend on the amount of product used.