General liability insurance is insurance against torts, which can be in the form of property damage, or injury to a customer or bystander. Say that you drop a tree and it lands the wrong way, and it crushes the house, and injures the customer inside. General liability insurance would pay to fix the house and pay for the customer's medical bills and pain and suffering (although if it hurt an employee, that would be a different story, and that would be covered by worker's compensation insurance, which you really should get if you have any employees, as it's usually required).
Bonding is very rare for tree service companies, and bonding is usually insurance against breach of contract rather than a tort. For instance, some companies take a percentage up-front as payment, such as 25-50% up front. It has happened where contractors steal the money, and don't perform the work. The customer could pursue the bonding company for compensation. Also, if a contractor provided below-standard quality work (such as didn't meet the specs of the contract by leaving large logs all over the place when the contract specified hauling them away), the customer could pursue the bonding company for the cost to complete the project. Unless your in a state or town where it's required, bonding is usually unnecessary, especially since most tree companies don't take any money up-front. The customer would just probably not pay you upon completion if you didn't complete the work as specified.
It would be unethical to say you're bonded when you don't have bonding. Just say you're fully insured, assuming you have General Liability Insurance, and Worker's Comp coverage on any employees you have, along with Commercial Auto Insurance. If they ask about bonding, be honest and tell them it's very rare for tree companies to be bonded and explain that since you aren't taking money up-front there's virtually no risk of them benefiting from bonding.
In terms of licensing, only eight states require tree service contractors be licensed.
https://occupationallicensing.com/occupation/tree-trimmer/
Some towns/cities may require tree service licenses, however, but they usually are fairly straightforward, with just providing a COI (some want to be listed as additionally insured), and paying $10-$100/yr, with no exam needed, and signing an indemnification agreement. If you have a DBA registered with your county, a DBA is in effect a "license", provided no further licenses are required. Also, if you have an LLC or Corporation, you are registered with your State Secretary of State, (unless you incorporate in another state, in which case, you probably need a foreign corporation designation in your state). If you have an LLC or corporation, you can say that you are "registered with the Texas (or whichever state you are in) Secretary of State, or just say "Registered and Fully Insured".
The ISA certification is mostly a voluntary, credential-boosting process, and isn't generally required, and it certainly is not a "license" in and of itself.
I hope this information helps.
